Knowledge Bank

The microwave spectrum of the methylacetylene $SO2(MASO2)$ complex has been observed using a pulsed nozzle, molecular beam Fourier transformer microwave spectrometer. Two different large amplitude internal motions were observed. The methyl group internal rotation splits each rotational transition of the complex into A and E components; an $SO2$ inversion motion further splits each A and E level into doublets. The structure of the complex was determined using the rotational constants of the normal species as well as MA $S18O16O$, and the dipole moment data. The $SO2$ was found to sit above the carbon-dioxide triple bond, with its symmetry axis twisted away from parallel to the symmetry axis of the methylacetylene by about $60\circ$. We are proceeding with the assignment of the E transitions and will report a global fit of all the rotational transitions.